How about the tried and true of good maintaince will give your trans a longer and more trouble free life???If your 4T65e trans needs fluid at 30-50k, it's either heavily abused or dying. These aren't TH350/400's or C4/6's that got ridden heavy & needed fresh grip, they're actually well-designed for their (stock) use, given proper driving habits and fluid cooling. The minimal "routine" clutch/band wear material is easily handled by the filter for 100-200k, as proven by millions on the road.
As long as the transmission doesn't already have issues, a 4T65E transgo kit is great for these cars. I think it helps the transmission shift optimally to reduce wear. Also improves the shift quality greatly particularly 1-2 shift.I worked at SuperFlow on transmission testing equipment for a couple of years and worked beside Larry Schaffer (of Shaffer Shifter fame).
As Jake and dezldave above showed, there are a wide range of opinions on this question.
The best advice that rings true to me is:
1. Change the fluid and filter at regular intervals UNLESS it is old and has a lot of grit in it already. You can lose shift characteristics by cleaning out the grit, but at that point, the trans is probably worn quite a bit and longevity has been compromised. That one is a hard call.
2. A flush is always a bad idea because you can force debris into the shift solenoids and cause them to fail pretty quickly.
3. I prefer using a bucket to catch old fluid from the trans cooler on the radiator and replace it as it drains out. Just hook up a hose to the fluid feed line (usually the upper line) and run the car for maybe 30 seconds then top it off with what you lost until the fluid runs clean. This way, you are pulling fluid from both the pan and also through the torque converter for a complete fluid change. If you use that method, you can leave a somewhat used filter in place or afterward drop the pan and replace the fluid lost in that process.
4. Lastly, you could just drop the pan to change the filter and be left with a mix of old and new fluid (what was left sitting in the TC and cooler). This decision has more to do with how dirty the fluid is to begin with.
My 2 cents.
Years ago I put a RAMCHARGERS shift kit in my 03 GTP SC. When I did that trans shift kit it worked better than I was hoping for. Under normal driving it has a slightly harder gear shift(1-2-3 and OD). When I did my shift kit install, I chose to go with one step down from hard shifting. Didn't want to create any internal breakage from real hard shifting. In my case it shifts pretty smooth......but when I get on the throttle it has a nice FIRM shift but no HARSH/POUNDING shifts......didn't want to break anything in the tranny. It's been several years now and it still works MOST EXCELLENT with zero issues. On another note, I'm not sure if one can find a RAMCHARGERS SHIFT KIT or not. ( I bought my kit from 3800 PRO). I also do trans fluid changes after 30K. For me I like the idea that I'm helping out with the overall trans life. After all these years it still works flawlessly.As long as the transmission doesn't already have issues, a 4T65E transgo kit is great for these cars. I think it helps the transmission shift optimally to reduce wear. Also improves the shift quality greatly particularly 1-2 shift.